Much work has been done to provide improved rackets for tennis and racquetball. The principal aim has been to provide rackets for achieving superior game performance, but another important concern has been to provide rackets which lessen the risk of injury, particularly damage to joints, e.g., tennis elbow. In the pursuit of improving the characteristics of rackets, much attention has been focused upon the stringed playing surfaces.
A prime example of earlier approaches by others is U.S. Pat No. 3,999,756, issued to Howard Head, which describes the famous and highly successful Head tennis racket. By careful experimental selection of a combination of size, geometry, mass, and materials, Head provides a racket with improved characteristics. However, the Head racket does not succeed in sufficiently improving the accuracy of balls which are struck off-axis.
In U.S. Pat No. 4,076,241, Newsome discloses a racket with an arrangement of strings providing a concave ball-engaging surface of dual string surfaces, intersecting each other along the center axis of the racket. Newsome's objective was to enable a player to maintain accuracy as the ball is hit away from the racket's sweet spot, while reducing twisting of the racket in the hand of the player. However, the dual string arrangement was not allowed by the U.S. Tennis Association for tournament play.
Another approach to enlarge the so-called "sweet spot" of the racket is disclosed in U.S. Pat. No. 4,330,132, issued to Ferrari. The central idea is to vary the tension of the individual string segments to make string deflection uniform in response to ball impact. However,, such rackets are exceedingly difficult to string.
Earlier tennis rackets had a generally narrower playing surface compared to modern rackets. Older tennis rackets also responded poorly to off-center axis hits, both in terms of "feel", as well as ball control. More modern rackets have a wider playing surface. Head, in particular, succeeded in enlarging the size of the "sweet spot", and hence improved the "feel" of off-center axis hits. However, control, especially in terms of elevation and direction of return shots for off-center axis hits remains a major issue for the wider rackets of today.
The present invention is the result of continued research, analysis, and extensive experimentation with tennis racket constructions aimed at further improvement in the playing characteristics and reduction of the torque transmitted to the player's hands and arms.
It is therefore an object of the invention to provide a racket with a string surface which provides improved control for off-center axis hits.
A still further object of the invention is to provide a racket construction which reduces the torque transmitted to the player's arm by spreading the energy of percussion over a larger period of time.
Another object of the invention is to provide a stringed surface which is planar but behaves dynamically as a bilaterally concave surface imparting an appropriate correcting vector to hit balls, but in a single planar surface weave and without doubling the webbing.
Still another object is to provide a racket having a strung surface whose dynamic behavior can more closely match the vibrational frequency of balls.
These and other objects are achieved by one or more of the following elements of racket construction.